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以锦屏Ⅰ级水电站为例,在实际地质调查基础上,分析整理实测地应力数据,以数值模拟为手段,对高地应力区复杂结构谷坡应力场特征进行了研究。结果表明:高地应力区具有复杂结构的河谷,遭受河谷快速下切改造后,其谷坡应力场存在“四区”分布特征,即应力降低区、应力过渡区、应力增高区及原始应力区;背景构造应力和河谷形态特征是导致谷底高地应力现象出现的2个重要因素;谷坡内的软弱带对应力场分布产生重大影响,尤其是倾坡外断层的存在,更易于谷坡应力卸荷,这是导致锦屏左岸深卸荷形成的重要原因,以及导致左岸卸荷基准面高程低于右岸的原因之一;河谷下切过程中,右岸顺倾岸坡发生应力调整的坡体范围比左岸的反倾岸坡大,因此其原始应力区在更深的深度内才出现。简单探讨了锦屏深裂缝的成因机制,认为河谷迅速下切导致的快速卸荷是锦屏深裂缝形成的原因之一。
Taking Jinping Ⅰ Hydropower Station as an example, based on the actual geologic survey, the measured geostress data are analyzed and collated, and the numerical simulation is taken as a measure to study the stress field characteristics of the valley slopes with complex structure in the high ground stress region. The results show that the valleys with complex structure in the high stress area have the characteristics of “four zones” after being rapidly undercut and reformed, that is, the stress reduction zone, the stress transition zone, the stress increasing zone and the original stress zone The background tectonic stress and valley shape are the two important factors which lead to the stress phenomenon in the valley bottom. The weak zone in the valley slope has a significant influence on the stress field distribution, especially the fault out-dip fault, This is one of the reasons leading to the formation of deep unloading in the left bank of Jinping and the reason that the elevation of unloading ground in the left bank is lower than that in the right bank. The anti-dump slope on the left bank is large, so its original stress zone appears only at deeper depths. The mechanism of the deep cracks in Jinping is briefly discussed. It is considered that the rapid unloading caused by the rapid river cutting is one of the reasons for the formation of deep cracks in Jinping.